Re: [Intel-gfx] [CI 15/19] drm/i915/bigjoiner: atomic commit changes for uncompressed joiner

["Manna, Animesh" <animesh.manna@intel.com>]

> -----Original Message-----
> From: Jani Nikula <jani.nikula@linux.intel.com>
> Sent: Thursday, June 3, 2021 3:10 PM
> To: Roper, Matthew D <matthew.d.roper@intel.com>; intel-
> gfx@lists.freedesktop.org
> Cc: Manna, Animesh <animesh.manna@intel.com>; Navare, Manasi D
> <manasi.d.navare@intel.com>; Kulkarni, Vandita <vandita.kulkarni@intel.com>
> Subject: Re: [Intel-gfx] [CI 15/19] drm/i915/bigjoiner: atomic commit changes
> for uncompressed joiner
> 
> On Fri, 14 May 2021, Matt Roper <matthew.d.roper@intel.com> wrote:
> > From: Animesh Manna <animesh.manna@intel.com>
> >
> > Respective bit for master or slave to be set for uncompressed
> > bigjoiner in dss_ctl1 register.
> 
> I was looking at the changes here due to a static checker complaint, and I think
> there are a number of issues here. Some more serious than others, and some
> predate the patch.
> 
> Comments inline.
> 
> > Cc: Manasi Navare <manasi.d.navare@intel.com>
> > Signed-off-by: Animesh Manna <animesh.manna@intel.com>
> > Signed-off-by: Clinton Taylor <Clinton.A.Taylor@intel.com>
> > Signed-off-by: Matt Roper <matthew.d.roper@intel.com>
> > Reviewed-by: Manasi Navare <manasi.d.navare@intel.com>
> > ---
> >  drivers/gpu/drm/i915/display/intel_display.c |  6 +++
> >  drivers/gpu/drm/i915/display/intel_vdsc.c    | 40 +++++++++++++++++++-
> >  drivers/gpu/drm/i915/display/intel_vdsc.h    |  2 +
> >  drivers/gpu/drm/i915/i915_reg.h              |  2 +
> >  4 files changed, 49 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/gpu/drm/i915/display/intel_display.c
> > b/drivers/gpu/drm/i915/display/intel_display.c
> > index b5fd721137d3..422b59ebf6dc 100644
> > --- a/drivers/gpu/drm/i915/display/intel_display.c
> > +++ b/drivers/gpu/drm/i915/display/intel_display.c
> > @@ -3411,6 +3411,7 @@ static void icl_ddi_bigjoiner_pre_enable(struct
> intel_atomic_state *state,
> >  					 const struct intel_crtc_state
> *crtc_state)  {
> >  	struct intel_crtc *master = to_intel_crtc(crtc_state->uapi.crtc);
> > +	struct drm_i915_private *dev_priv = to_i915(master->base.dev);
> >  	struct intel_crtc_state *master_crtc_state;
> >  	struct drm_connector_state *conn_state;
> >  	struct drm_connector *conn;
> > @@ -3444,6 +3445,9 @@ static void icl_ddi_bigjoiner_pre_enable(struct
> intel_atomic_state *state,
> >  		/* and DSC on slave */
> >  		intel_dsc_enable(NULL, crtc_state);
> >  	}
> > +
> > +	if (DISPLAY_VER(dev_priv) >= 13)
> > +		intel_uncompressed_joiner_enable(crtc_state);
> >  }
> >
> >  static void hsw_crtc_enable(struct intel_atomic_state *state, @@
> > -6250,6 +6254,8 @@ static bool hsw_get_pipe_config(struct intel_crtc *crtc,
> >  	}
> >
> >  	intel_dsc_get_config(pipe_config);
> > +	if (DISPLAY_VER(dev_priv) >= 13 && !pipe_config-
> >dsc.compression_enable)
> > +		intel_uncompressed_joiner_get_config(pipe_config);
> >
> >  	if (!active) {
> >  		/* bigjoiner slave doesn't enable transcoder */ diff --git
> > a/drivers/gpu/drm/i915/display/intel_vdsc.c
> > b/drivers/gpu/drm/i915/display/intel_vdsc.c
> > index adcd6752f919..efc3184d8315 100644
> > --- a/drivers/gpu/drm/i915/display/intel_vdsc.c
> > +++ b/drivers/gpu/drm/i915/display/intel_vdsc.c
> > @@ -1021,6 +1021,22 @@ static i915_reg_t dss_ctl2_reg(const struct
> intel_crtc_state *crtc_state)
> >  	return is_pipe_dsc(crtc_state) ? ICL_PIPE_DSS_CTL2(pipe) : DSS_CTL2;
> > }
> >
> > +void intel_uncompressed_joiner_enable(const struct intel_crtc_state
> > +*crtc_state)
> 
> Naming. Basically for any new function, the function name prefix should match
> the file name. intel_vdsc.[ch] should have functions prefixed intel_vdsc_*(). This
> is where we're headed to increase clarity.
> 
> intel_uncompressed_*() is something completely different.
> 
> Granted, here we already have intel_dsc_*() in intel_vdsc.c. We should probably
> stick with intel_dsc_*(). A possible function or file rename is not out of the
> question, but that's a separate matter.

As there is not separate register for uncompressed joiner, using bitfield of dsc register only the function name can be changed to intel_dsc_uncompressed_joiner_enable().

> 
> > +{
> > +	struct intel_crtc *crtc = to_intel_crtc(crtc_state->uapi.crtc);
> > +	struct drm_i915_private *dev_priv = to_i915(crtc->base.dev);
> > +	u32 dss_ctl1_val = 0;
> > +
> > +	if (crtc_state->bigjoiner && !crtc_state->dsc.compression_enable) {
> > +		if (crtc_state->bigjoiner_slave)
> > +			dss_ctl1_val |= UNCOMPRESSED_JOINER_SLAVE;
> > +		else
> > +			dss_ctl1_val |= UNCOMPRESSED_JOINER_MASTER;
> > +
> > +		intel_de_write(dev_priv, dss_ctl1_reg(crtc_state), dss_ctl1_val);
> > +	}
> > +}
> > +
> >  void intel_dsc_enable(struct intel_encoder *encoder,
> >  		      const struct intel_crtc_state *crtc_state)  { @@ -1060,13
> > +1076,35 @@ void intel_dsc_disable(const struct intel_crtc_state
> *old_crtc_state)
> >  	struct intel_crtc *crtc = to_intel_crtc(old_crtc_state->uapi.crtc);
> >  	struct drm_i915_private *dev_priv = to_i915(crtc->base.dev);
> >
> > -	if (!old_crtc_state->dsc.compression_enable)
> > +	if (!(old_crtc_state->dsc.compression_enable &&
> > +	      old_crtc_state->bigjoiner))
> 
> This fails to disable compression if we only have compression but no bigjoiner,
> which is the more common case!
> 
> See also:
> 
> https://gitlab.freedesktop.org/drm/intel/-/issues/3537
> https://patchwork.freedesktop.org/patch/msgid/20210603065356.15435-1-
> vandita.kulkarni@intel.com
> 

We may need to remove both the condition check.
In uncompressed bigjoiner, compression_enable flag will be 0 and may not clear the bit of dss_ctl1_reg.
So can we remove both the checks, hoping it will not harm reseting the register even if it is not set. 

> >  		return;
> >
> >  	intel_de_write(dev_priv, dss_ctl1_reg(old_crtc_state), 0);
> >  	intel_de_write(dev_priv, dss_ctl2_reg(old_crtc_state), 0);  }
> >
> > +void intel_uncompressed_joiner_get_config(struct intel_crtc_state
> > +*crtc_state) {
> > +	struct intel_crtc *crtc = to_intel_crtc(crtc_state->uapi.crtc);
> > +	struct drm_i915_private *dev_priv = to_i915(crtc->base.dev);
> > +	u32 dss_ctl1;
> > +
> > +	dss_ctl1 = intel_de_read(dev_priv, dss_ctl1_reg(crtc_state));
> > +	if (dss_ctl1 & UNCOMPRESSED_JOINER_MASTER) {
> > +		crtc_state->bigjoiner = true;
> > +		if (!WARN_ON(INTEL_NUM_PIPES(dev_priv) == crtc->pipe + 1))
> > +			crtc_state->bigjoiner_linked_crtc =
> > +				intel_get_crtc_for_pipe(dev_priv, crtc->pipe +
> 1);
> > +	} else if (dss_ctl1 & UNCOMPRESSED_JOINER_SLAVE) {
> > +		crtc_state->bigjoiner = true;
> > +		crtc_state->bigjoiner_slave = true;
> > +		if (!WARN_ON(crtc->pipe == PIPE_A))
> > +			crtc_state->bigjoiner_linked_crtc =
> > +				intel_get_crtc_for_pipe(dev_priv, crtc->pipe -
> 1);
> > +	}
> 
> Nitpick: This duplicates a bunch of logic for figuring out master/slave.
> 
> The static checker warning was about crtc->pipe + 1 usage. Since
> INTEL_NUM_PIPES() looks at the hamming weight of i915->pipe_mask, the
> checker has a hard time figuring out it does not overflow
> i915->pipe_to_crtc_mapping[] in intel_get_crtc_for_pipe().
> 
> So here in intel_vdsc.c the checks are for overflowing/underflowing the pipe
> range. In intel_get_crtc_for_pipe() there's a check for the pipe actually existing -
> the pipe numbering might not be contiguous.
> 
> Superficially the static checker warning is bogus, as in we won't overflow
> anything. However, deep down there are issues in the consistency of the checks
> and how to handle non-contigouous pipe numbering.
> 
> Indeed, this does not *need* the number. We should figure out the next *crtc*,
> not the next pipe *number*, which may or may not be pipe + 1.

dss_ctl1 value is used to identify master or slave crtc. If needed WARN_ON check can be removed... but pipe enum values like PIPE_A/B/C/D is used to get the master/slave crtc and always bigjoiner is possible with two adjacent pipes.

Regards,
Animesh

> 
> 
> BR,
> Jani.
> 
> > +}
> > +
> >  void intel_dsc_get_config(struct intel_crtc_state *crtc_state)  {
> >  	struct drm_dsc_config *vdsc_cfg = &crtc_state->dsc.config; diff
> > --git a/drivers/gpu/drm/i915/display/intel_vdsc.h
> > b/drivers/gpu/drm/i915/display/intel_vdsc.h
> > index 65d301c23580..fe4d45561253 100644
> > --- a/drivers/gpu/drm/i915/display/intel_vdsc.h
> > +++ b/drivers/gpu/drm/i915/display/intel_vdsc.h
> > @@ -12,11 +12,13 @@ struct intel_encoder;  struct intel_crtc_state;
> >
> >  bool intel_dsc_source_support(const struct intel_crtc_state
> > *crtc_state);
> > +void intel_uncompressed_joiner_enable(const struct intel_crtc_state
> > +*crtc_state);
> >  void intel_dsc_enable(struct intel_encoder *encoder,
> >  		      const struct intel_crtc_state *crtc_state);  void
> > intel_dsc_disable(const struct intel_crtc_state *crtc_state);  int
> > intel_dsc_compute_params(struct intel_encoder *encoder,
> >  			     struct intel_crtc_state *pipe_config);
> > +void intel_uncompressed_joiner_get_config(struct intel_crtc_state
> > +*crtc_state);
> >  void intel_dsc_get_config(struct intel_crtc_state *crtc_state);  enum
> > intel_display_power_domain  intel_dsc_power_domain(const struct
> > intel_crtc_state *crtc_state); diff --git
> > a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
> > index 31bc413dbba1..dd6e0bae9573 100644
> > --- a/drivers/gpu/drm/i915/i915_reg.h
> > +++ b/drivers/gpu/drm/i915/i915_reg.h
> > @@ -11493,6 +11493,8 @@ enum skl_power_gate {
> >  #define  SPLITTER_CONFIGURATION_MASK		REG_GENMASK(26, 25)
> >  #define  SPLITTER_CONFIGURATION_2_SEGMENT
> 	REG_FIELD_PREP(SPLITTER_CONFIGURATION_MASK, 0)
> >  #define  SPLITTER_CONFIGURATION_4_SEGMENT
> 	REG_FIELD_PREP(SPLITTER_CONFIGURATION_MASK, 1)
> > +#define  UNCOMPRESSED_JOINER_MASTER		(1 << 21)
> > +#define  UNCOMPRESSED_JOINER_SLAVE		(1 << 20)
> >
> >  #define _ICL_PIPE_DSS_CTL2_PB			0x78204
> >  #define _ICL_PIPE_DSS_CTL2_PC			0x78404
> 
> --
> Jani Nikula, Intel Open Source Graphics Center
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